Fabrication of vertical field effect transistor structure with strained channels

ABSTRACT

A method of forming a vertical fin field effect transistor (vertical finFET) with a strained channel, including forming one or more vertical fins on a substrate, forming a sacrificial stressor layer adjacent to the one or more vertical fins, wherein the sacrificial stressor layer imparts a strain in the adjacent vertical fins, forming a fin trench through one or more vertical fins and the sacrificial stressor layer to form a plurality of fin segments and a plurality of sacrificial stressor layer blocks, forming an anchor wall adjacent to and in contact with one or more fin segment endwalls, and removing at least one of the plurality of the sacrificial stressor layer blocks, wherein the anchor wall maintains the strain of the adjacent fin segments after removal of the sacrificial stressor layer blocks adjacent to the fin segment with the adjacent anchor wall.

BACKGROUND Technical Field

The present invention relates to fabricating a vertical field effecttransistor (VFET) structure with a strained channel, and moreparticularly to controlling a strain in a channel material for a VFET byutilizing a sacrificial stressor material and a stressor anchor materialto impose a channel material strain.

Description of the Related Art

A Field Effect Transistor (FET) typically has a source, a channel, and adrain, where current flows from the source to the drain, and a gate thatcontrols the flow of current through the channel. Field EffectTransistors (FETs) can have a variety of different structures, forexample, FETs have been fabricated with the source, channel, and drainformed in the substrate material itself, where the current flowshorizontally (i.e., in the plane of the substrate), and finFETs havebeen formed with the channel extending outward from the substrate, butwhere the current also flows horizontally from a source to a drain. Thechannel for the finFET can be an upright slab of thin rectangular Si,commonly referred to as the fin with a gate on the fin, as compared to aMOSFET with a single gate in the plane of the substrate. Depending onthe doping of the source and drain, an n-FET or a p-FET may be formed.

Examples of FETs can include a metal-oxide-semiconductor field effecttransistor (MOSFET) and an insulated-gate field-effect transistor(IGFET). Two FETs also may be coupled to form a complementary metaloxide semiconductor (CMOS), where a p-channel MOSFET and n-channelMOSFET are coupled together.

With ever decreasing device dimensions, forming the individualcomponents and electrical contacts become more difficult. An approach istherefore needed that retains the positive aspects of traditional FETstructures, while overcoming the scaling issues created by formingsmaller device components.

SUMMARY

A method of forming a vertical fin field effect transistor (verticalfinFET) with a strained channel, including forming one or more verticalfins on a substrate, forming a sacrificial stressor layer adjacent tothe one or more vertical fins, wherein the sacrificial stressor layerimparts a strain in the adjacent vertical fins, forming a fin trenchthrough one or more vertical fins and the sacrificial stressor layer toform a plurality of fin segments and a plurality of sacrificial stressorlayer blocks, forming an anchor wall adjacent to and in contact with oneor more fin segment endwalls, and removing at least one of the pluralityof the sacrificial stressor layer blocks, wherein the anchor wallmaintains the strain of the adjacent fin segments after removal of thesacrificial stressor layer blocks adjacent to the fin segment with theadjacent anchor wall.

A method of forming a vertical finFET with a strained channel, includingforming a plurality of vertical fins on a substrate, forming asacrificial stressor layer adjacent to the vertical fins, wherein thesacrificial stressor layer is in contact with the sidewalls of theadjacent vertical fins, and imparts a strain to the adjacent verticalfins, forming a plurality of fin trenches through the plurality ofvertical fins and the sacrificial stressor layer, where the fin trenchseparates the vertical fins into columns of fin segments and a pluralityof sacrificial stressor layer blocks adjacent to two fin segments,forming an anchor wall in each fin trench adjacent to and in contactwith one or more fin segment endwalls, and removing the plurality of thesacrificial stressor layer blocks, wherein the anchor wall maintains thestrain of the adjacent fin segments after removal of the sacrificialstressor layer blocks adjacent to the fin segment with the adjacentanchor wall.

A vertical fin field effect transistor (finFET), including one or morevertical fins formed on a substrate, a doped region in the substratelocated below at least one of the one or more vertical fins, an anchorwall at each end of the one or more vertical fins, where the anchor wallis in contact with the endwall of the vertical fin, and where the anchorwall maintains the vertical fin in a strained state, a bottom spacer onthe substrate and adjacent the sidewall of at least one of the one ormore vertical fins, a gate structure on at least a portion of thesidewalls of at least one of the one or more vertical fins, and a topspacer on the gate structure opposite the bottom spacer.

These and other features and advantages will become apparent from thefollowing detailed description of illustrative embodiments thereof,which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The disclosure will provide details in the following description ofpreferred embodiments with reference to the following figures wherein:

FIG. 1 is a cross-sectional side view of a substrate in accordance withan exemplary embodiment;

FIG. 2 is a cross-sectional side view of a substrate with a hardmasklayer and a photo mask layer in accordance with an exemplary embodiment;

FIG. 3 is a cross-sectional side view of a photo mask layer patterned onthe hardmask layer in accordance with an exemplary embodiment;

FIG. 4 is a cross-sectional side view of a hardmask fin template andphoto mask block on the substrate in accordance with an exemplaryembodiment;

FIG. 5 is a cross-sectional side view of a hardmask fin template on thesubstrate in accordance with an exemplary embodiment;

FIG. 6 is a cross-sectional side view of a hardmask fin template on avertical fin on the substrate in accordance with an exemplaryembodiment;

FIG. 7 is a cross-sectional side view of a sacrificial stressor layerover the hardmask fin template(s), and vertical fin(s) in accordancewith an exemplary embodiment;

FIG. 8 is a perspective view of the cross-section of the sacrificialstressor layer on the sidewalls of hardmask fin template(s), andvertical fin(s) shown in FIG. 7 in accordance with an exemplaryembodiment;

FIG. 9 is a perspective view of a cross-section of a fin-cut mask formedon the surface of the sacrificial stressor layer and the hardmask fintemplate(s) in accordance with an exemplary embodiment;

FIG. 10 is a cross-sectional side view of a fin-cut mask on asacrificial stressor layer and hardmask fin template(s) in accordancewith an exemplary embodiment;

FIG. 11 is a perspective view of a cross-section of a fin trench througha fin-cut mask, vertical fins, hardmask fin templates, and sacrificialstressor layer in accordance with an exemplary embodiment;

FIG. 12 is a perspective view of a cross-section of a fin trench throughthe vertical fins, hardmask fin templates, and sacrificial stressorlayer after removal of the fin-cut mask in accordance with an exemplaryembodiment;

FIG. 13 is a perspective view of a cross-section of an anchor wallformed in the fin trenches adjacent to the vertical fins in accordancewith an exemplary embodiment;

FIG. 14 is a perspective view of a cross-section of the anchor walls incontact with the fin segment endwalls, and exposed fin sidewalls afterremoval of sacrificial stressor layer blocks in accordance with anexemplary embodiment;

FIG. 15 is a perspective view of a cross-section of the anchor walls incontact with the fin segment endwalls, and the exposed fin sidewalls,after removal of the hardmask fin templates in accordance with anexemplary embodiment;

FIG. 16 is a cross-sectional side view of a doped region and a bottomspacer layer on the substrate between a plurality of fin segments inaccordance with an exemplary embodiment; and

FIG. 17 is a cross-sectional side view of a gate structure and topsource/drains formed on the plurality of fin segments in accordance withan exemplary embodiment.

DETAILED DESCRIPTION

Principles and embodiments of the present disclosure relate generally toan approach to fabricate a vertical field effect transistor (VFET), ormore specifically a vertical fin field effect transistor (verticalfinFET), where current flows vertically through the channel, includingcreating and maintaining the VFET channel in a strained state. Amaterial with different properties, such as different coefficients ofthermal expansion (CTE) and/or different lattice constants may be usedto impart a strain in the vertical fin, and/or a second material may beused to anchor the vertical fin in the strained state. A verticalcompressive or tensile stress may be applied to the vertical fin by anadjacent material.

Principles and embodiments also relate to forming one or more verticalfin field effect transistor (vertical finFETs) with a vertical channelstructure having an increased carrier mobility and/or increased drivecurrent in the channel(s) of the one or more vertical finFETs due to animparted strain. In one or more embodiments, a sacrificial stressormaterial may be formed adjacent to one or more vertical fins, where thedifference between the coefficient of thermal expansion of thesacrificial stressor material and the coefficient of thermal expansionof the vertical fin material can determine the amount of strain inducedin the vertical fin(s). An anchor wall may be formed in contact with anend face of the one or more vertical fins to maintain the fins in astrained state after removal of the sacrificial stressor material due toan internal stress.

It has been found that maintaining a strain in a vertical fin can bevery difficult due to various relaxation mechanisms available to avertical fin due to the fin alignment and geometry. A vertical fin maybecome relaxed regardless of its initial strain status because unlike atypical MOSFET a vertical fin typically is free-standing and not incontact with a material (e.g., substrate) that consistently applies ormaintains a stress. An approach to maintaining a strain in a verticalfin can involve having opposing vertical surfaces of the vertical fin incontact with a material that physically keeps the fin in a strainedstate without interfering with other features of the semiconductordevice.

It is to be understood that the present invention will be described interms of a given illustrative architecture; however, otherarchitectures, structures, substrate materials and process features andsteps may be varied within the scope of the present invention.

It will also be understood that when an element such as a layer, regionor substrate is referred to as being “on” or “over” another element, itcan be directly on the other element or intervening elements may also bepresent. In contrast, when an element is referred to as being “directlyon” or “directly over” another element, there are no interveningelements present. It will also be understood that when an element isreferred to as being “connected” or “coupled” to another element, it canbe directly connected or coupled to the other element or interveningelements may be present. In contrast, when an element is referred to asbeing “directly connected” or “directly coupled” to another element,there are no intervening elements present.

The present embodiments may include a design for an integrated circuitchip, which may be created in a graphical computer programming language,and stored in a computer storage medium (such as a disk, tape, physicalhard drive, or virtual hard drive such as in a storage access network).If the designer does not fabricate chips or the photolithographic masksused to fabricate chips, the designer may transmit the resulting designby physical means (e.g., by providing a copy of the storage mediumstoring the design) or electronically (e.g., through the Internet) tosuch entities, directly or indirectly. The stored design is thenconverted into the appropriate format (e.g., GDSII) for the fabricationof photolithographic masks, which typically include multiple copies ofthe chip design in question that are to be formed on a wafer. Thephotolithographic masks are utilized to define areas of the wafer(and/or the layers thereon) to be etched or otherwise processed.

Methods as described herein may be used in the fabrication of integratedcircuit chips. The resulting integrated circuit chips can be distributedby the fabricator in raw wafer form (that is, as a single wafer that hasmultiple unpackaged chips), as a bare die, or in a packaged form. In thelatter case the chip is mounted in a single chip package (such as aplastic carrier, with leads that are affixed to a motherboard or otherhigher level carrier) or in a multichip package (such as a ceramiccarrier that has either or both surface interconnections or buriedinterconnections). In any case the chip is then integrated with otherchips, discrete circuit elements, and/or other signal processing devicesas part of either (a) an intermediate product, such as a motherboard, or(b) an end product. The end product can be any product that includesintegrated circuit chips, ranging from toys and other low-endapplications to advanced computer products having a display, a keyboardor other input device, and a central processor.

Reference in the specification to “one embodiment” or “an embodiment” ofthe present principles, as well as other variations thereof, means thata particular feature, structure, characteristic, and so forth describedin connection with the embodiment is included in at least one embodimentof the present principles. Thus, the appearances of the phrase “in oneembodiment” or “in an embodiment”, as well any other variations,appearing in various places throughout the specification are notnecessarily all referring to the same embodiment.

It is to be appreciated that the use of any of the following “/”,“and/or”, and “at least one of”, for example, in the cases of “A/B”, “Aand/or B” and “at least one of A and B”, is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of both options (A andB). As a further example, in the cases of “A, B, and/or C” and “at leastone of A, B, and C”, such phrasing is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of the third listedoption (C) only, or the selection of the first and the second listedoptions (A and B) only, or the selection of the first and third listedoptions (A and C) only, or the selection of the second and third listedoptions (B and C) only, or the selection of all three options (A and Band C). This may be extended, as readily apparent by one of ordinaryskill in this and related arts, for as many items listed.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises,” “comprising,” “includes” and/or “including,” when usedherein, specify the presence of stated features, integers, steps,operations, elements and/or components, but do not preclude the presenceor addition of one or more other features, integers, steps, operations,elements, components and/or groups thereof.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”upper, and the like, may be used herein for ease of description todescribe one element's or feature's relationship to another element(s)or feature(s) as illustrated in the FIGS. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the FIGS. For example, if the device in theFIGS. is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the term “below” can encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations), and the spatially relativedescriptors used herein may be interpreted accordingly. In addition, itwill also be understood that when a layer is referred to as being“between” two layers, it can be the only layer between the two layers,or one or more intervening layers may also be present.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another element. Thus, a first element discussed belowcould be termed a second element without departing from the scope of thepresent concept.

While exemplary embodiments have been shown for a particular device, itshould be understood that a plurality of such devices may be arrangedand/or fabricated on a substrate to form integrated devices that may beintegrated onto a substrate, for example through very large scaleintegration to produce complex devices such a central processing units(CPUs) and application specific integrated circuits (ASICs). The presentembodiments may be part of a device or circuit, and the circuits asdescribed herein may be part of a design for an integrated circuit chip.

Referring now to the drawings in which like numerals represent the sameor similar elements and initially to FIG. 1, which is a cross-sectionalside view of a substrate in accordance with an exemplary embodiment.

In one or more embodiments, a substrate 110 may be a semiconductor or aninsulator with an active surface semiconductor layer. The substrate maybe crystalline, semi-crystalline, microcrystalline, or amorphous. Thesubstrate may be essentially (i.e., except for contaminants) a singleelement (e.g., silicon), primarily (i.e., with doping) of a singleelement, for example, silicon (Si) or germanium (Ge), or the substratemay include a compound, for example, Al₂O₃, SiO₂, GaAs, SiC, or SiGe.The substrate may also have multiple material layers, for example, asemiconductor-on-insulator substrate (SeOI), a silicon-on-insulatorsubstrate (SOI), germanium-on-insulator substrate (GeOI), orsilicon-germanium-on-insulator substrate (SGOI). The substrate may alsohave other layers forming the substrate, including high-k oxides and/ornitrides. In one or more embodiments, the substrate 110 may be a siliconwafer. In an embodiment, the substrate may be a single crystal silicon(Si), silicon germanium (SiGe), or III-V semiconductor (e.g., GaAs)wafer, or have a single crystal silicon (Si), silicon germanium (SiGe),or III-V semiconductor (e.g., GaAs) surface/active layer.

FIG. 2 is a cross-sectional side view of a substrate with a hardmasklayer and a photo mask layer in accordance with an exemplary embodiment.

In one or more embodiments, a hardmask layer 120 may be formed on anexposed surface of the substrate 110. A photo mask layer 130 may beformed on the exposed surface of the hardmask layer 120. In variousembodiments, the hardmask layer may be an oxide, for example, siliconoxide (SiO), a nitride, for example, a silicon nitride (SiN), or anoxynitride, for example, silicon oxynitride (SiON), or combinationsthereof. In various embodiments, the hardmask layer 120 may be siliconnitride (SiN), for example, Si₃N₄. The hard mask layer may also beformed by a thermal process, such as, for example, oxidation ornitridation of the top semiconductor layer. A combination of the variousprocesses may also be used to form hardmask layer 120.

In various embodiments, a photo mask layer 130 may be a temporary resist(e.g., PMMA) that may be deposited on the hardmask layer 120, patterned,and developed to expose portions of the hardmask layer 120. The photomask layer 130 may be a positive resist or a negative resist.

In various embodiments, the hardmask layer 120 may have a thickness inthe range of about 20 nm to about 80 nm, or in the range of about 30 nmto about 60 nm, or in the range of about 40 nm to about 50 nm, althoughother thicknesses are contemplated.

FIG. 3 is a cross-sectional side view of a photo mask layer patterned onthe hardmask layer in accordance with an exemplary embodiment.

In one or more embodiments, the photo mask layer 130 may be patternedand developed to form photo mask blocks 131 covering at least a portionof the surface of the hardmask layer 120. Portions of the photo masklayer 130 may be removed to form the photo mask blocks 131 and exposeunderlying portions of the hardmask layer 120. The photo mask blocks mayprotect the covered portion of the hardmask layer 120, while exposedportions of the hardmask layer 120 may be etched to form hardmask fintemplates on the substrate 110. One or more photo mask blocks 131 maydefine the width, length, and pitch of the one or more hardmask fintemplates and thereby, the width, length, and pitch of the one or morevertical fins.

In one or more embodiments, the photo mask blocks 131 may have a widthin the range of about 6 nm to about 20 nm, or may have a width in therange of about 8 nm to about 15 nm, or may have a width in the range ofabout 10 nm to about 12 nm. The photo mask blocks 131 may have a lengthin the range of about 100 nm to about 1000 nm, or in the range of about100 nm to about 500 nm, or in the range of about 100 nm to about 400 nm,or in the range of about 100 nm to about 200 nm.

In various embodiments, there may be a pitch between adjacent photo maskblocks 131 in the range of about 30 nm to about 200 nm, or in the rangeof about 30 nm to about 100 nm, or in the range of about 30 nm to about50 nm, or about 42 nm.

FIG. 4 is a cross-sectional side view of a hardmask fin template andphoto mask block on the substrate in accordance with an exemplaryembodiment.

In one or more embodiments, the hardmask layer 120 may be etched to formone or more hardmask fin template(s) 121, where the photo mask blocks131 defined the width, length, and location of the hardmask fintemplate(s) 121 on the substrate 110.

In various embodiments, the hardmask fin template(s) 121 may have apitch in the range of about 30 nm to about 200 nm, or in the range ofabout 30 nm to about 100 nm, or in the range of about 30 nm to about 50nm, or about 42 nm.

FIG. 5 is a cross-sectional side view of a hardmask fin template on thesubstrate in accordance with an exemplary embodiment.

In one or more embodiments, the photo mask blocks 131 may be removed toexpose the top surface(s) of the one or more hardmask fin template(s)121. The photo mask blocks 131 may be removed by known strippingmethods. In one or more embodiments, the hardmask fin template(s) 121may have a width in the range of about 6 nm to about 20 nm, or may havea width in the range of about 8 nm to about 15 nm, or may have a widthin the range of about 10 nm to about 12 nm.

FIG. 6 is a cross-sectional side view of a hardmask fin template on avertical fin on the substrate in accordance with an exemplaryembodiment.

In one or more embodiments, a vertical fin 111 may be formed from thesubstrate 110 by etching the substrate between the hardmask fintemplate(s) 121. In various embodiments, the substrate may be etchedusing a dry plasma etch, where the substrate may be etched by reactiveion etching (RIE) to provide a directional etch with control of sidewalletching.

In various embodiments, a sidewall image transfer (SIT) technique may beused to form one or more vertical fins 111 on the substrate. In atypical SIT process, spacers are formed on the sidewall of a sacrificialmandrel. The sacrificial mandrel is removed and the remaining uprightspacers are used as hardmask fin template(s) 121 to etch the topsemiconductor layer and form one or more vertical fins 111. The uprightspacers are then removed after the semiconductor vertical fins 111 havebeen formed. In various embodiments, the substrate may be a singlecrystal Si substrate and the vertical fins may be single crystalsilicon.

The vertical fins 111 may be doped, and may form the channel of avertical finFET, where the current flows in a vertical direction. AfinFET device with a strained channel may have an increase drivecurrent, and carrier (e.g., electron, hole) mobility.

In various embodiments, the fins 111 may have a width in the range ofabout 6 nm to about 20 nm, or may have a width in the range of about 8nm to about 15 nm, or in the range of about 10 nm to about 12 nm.

In various embodiments, the fins may have a height in the range of about25 nm to about 75 nm, or in the range of about 40 nm to about 50 nm.

In one or more embodiments, a doped region (i.e., source/drain region)(not shown) may be formed in the substrate 110. The doped region may beformed in-situ or ex-situ below the vertical fin(s) 111. The dopant maybe provided to the doped region(s) (i.e., source/drain region(s)) by ionimplantation, and source/drains formed by annealing the doped region(s).In various embodiments, the doped region may be n-doped or p-doped. Thedoped region may form a bottom source/drain. One or more doped regionsmay be formed in the substrate above which each of the one or morevertical fins may be formed, wherein the doped region forms a bottomsource/drain for a vertical field effect transistor.

It should be noted that the source and drain can be interchanged betweenthe top and bottom locations of a vertical fin, where the doped regionin the substrate may act as a source or a drain.

In various embodiments, the materials and layers may be deposited byphysical vapor deposition (PVD), chemical vapor deposition (CVD), atomiclayer deposition (ALD), molecular beam epitaxy (MBE), or any of thevarious modifications thereof, for example plasma-enhanced chemicalvapor deposition (PECVD), metal-organic chemical vapor deposition(MOCVD), low pressure chemical vapor deposition (LPCVD), electron-beamphysical vapor deposition (EB-PVD), and plasma-enhanced atomic layerdeposition (PE-ALD). The depositions may be epitaxial processes, and thedeposited material may be crystalline. In various embodiments, formationof a layer may be by one or more deposition processes, where, forexample, a conformal layer may be formed by a first process (e.g., ALD,PE-ALD, etc.) and a fill may be formed by a second process (e.g., CVD,electrodeposition, PVD, etc.).

FIG. 7 is a cross-sectional side view of a sacrificial stressor layerover the hardmask fin template(s), and vertical fin(s) in accordancewith an exemplary embodiment.

In one or more embodiments, a sacrificial stressor layer 140 may beformed on the exposed surface of the substrate 110. The sacrificialstressor layer 140 may be an oxide, for example, a flowable siliconoxide (SiO), a nitride, for example, a silicon nitride (SiN), or anoxynitride, for example, silicon oxynitride (SiON).

In one or more embodiments, sacrificial stressor layer 140 may be afilm, such as silicon nitride (SiN) deposited on at least a portion ofthe exposed surface of substrate 110, where the SiN may create either acompressive or tensile stress depending on the deposition parameters andthe hydrogen content of the SiN film. For example, in an exemplaryembodiment, the hydrogen concentration of an SiN film may be adjusted tocontrol the compressive or tensile stress generated by the SiN film dueto film density. In various embodiments, the SiN film may be depositedby a plasma-enhanced CVD (PECVD) processes, where a dual frequencycapacitively coupled chamber may be used to control the resultingtensile or compressive stresses. In various embodiments, the pressure ofthe reactants during formation may be adjusted to control the resultingtensile or compressive stresses of the deposited film, where higherpressures (e.g., >10 torr) may be used to generate a tensile stress, orlower pressures (e.g., 1-3 torr) may be used to generate compressivestresses. The hydrogen concentration may be controlled to effect thedensity and compressive stress of the deposited SiN film, where acompressively stressed film has a higher hydrogen concentration.

In various embodiments, a flowable oxide (FOX) may be applied to thesubstrate 110 by spin-coating followed by a thermal anneal to densifythe FOX and form sacrificial stressor layer 140. In various embodiments,the flowable oxide may be Spin-on glass (SOG), where SOG can be asilicon oxide suspended in a solvent.

In various embodiments, a two stage oxide deposition process may beperformed to deposit an oxide, which may be etched back by RIE, andanother deposit of the oxide may be performed again to form sacrificialstressor layer 140. Flowable oxides, high aspect ratio processes (HARP),enhanced high aspect ratio processes (eHARP), and other techniques maybe used to fill the area between the vertical fins 111.

In various embodiments, sacrificial stressor layer 140 may be an oxidedeposited by atomic layer deposition (ALD) or low-pressure chemicalvapor deposition (LPCVD). In an exemplary embodiment, the flowable oxidemay be utilized as the sacrificial stressor layer 140. The FOX flowsinto the gaps between the vertical fins 111 to provide a uniform surfacecoverage.

In one or more embodiments, the sacrificial stressor layer 140 may bedeposited over the substrate 110, vertical fin(s) 111, and hardmask fintemplate(s) 121 by a CVD process, where the sacrificial stressormaterial forming the sacrificial stressor layer 140 may be blanketdeposited. The sacrificial stressor layer 140 may fill in the spacebetween each of the vertical fins 111 and hardmask fin templates 121,and may be in contact with the sidewalls of the vertical fins 111 andhardmask fin templates 121. In various embodiments, the sacrificialstressor layer 140 may be in direct contact with the sidewalls of thevertical fins 111 and hardmask fin templates 121, where “direct contact”means that a first element, such as a first structure, and a secondelement, such as a second structure, are connected without anyintermediary conducting, insulating or semiconductor layers at theinterface of the two elements. The sacrificial stressor layer 140 mayextend above the top surface of the hardmask fin template(s) 121.

In one or more embodiments, the sacrificial stressor layer 140 may beheat treated (e.g., annealed) to reduce the volume of the as-depositedsacrificial stressor material, where the reduction in volume may apply acompressive stress to the vertical fin(s) 111 in contact with thesacrificial stressor layer 140. In various embodiments, the sacrificialstressor layer 140 may be annealed at a temperature in the range ofabout 300° C. to about 700° C., although lower and higher temperaturecan be used to anneal and cure the as deposited sacrificial stressorlayer 140.

In one or more embodiments, a sacrificial stressor layer 140 maycontract less than an adjacent vertical fin 111 during cooling (due todifferences in CTE) to apply a net tensile stress and impart a tensilestrain in the vertical fin(s) 111 in contact with the sacrificialstressor layer 140. In various embodiments, the sacrificial stressorlayer 140 may be exposed to a UV cure and/or undergo a high temperatureanneal to increase tension and decrease compression, where the UV cureand/or high temperature anneal is sufficient to reduce the hydrogenconcentration and/or generate additional Si—N bonds. High tensile stressvalues may be achieved at temperature of about 500° C. to about 700° C.

In various embodiments, the sacrificial stressor layer 140 may bechemically-mechanically polished (CMP) to reduce the height of thesacrificial stressor layer 140 to the top surface of the hardmask fintemplate(s) 121. The CMP may be continued to reduce the height of thesacrificial stressor layer 140 and the hardmask fin template(s) 121 toprovide a uniform flat surface.

FIG. 8 is a perspective view of the cross-section of the sacrificialstressor layer on the sidewalls of hardmask fin template(s), andvertical fin(s) shown in FIG. 7 in accordance with an exemplaryembodiment.

In one or more embodiments, the sacrificial stressor layer 140 fills thegaps between the vertical fins 111 and hardmask fin templates 121, wherethe sacrificial stressor layer 140 applies a compressive or tensilestress to at least the fin sidewalls 112 of one or more vertical fins111. The sacrificial stressor layer 140 may pull the fin sidewall(s) 112towards the surface of the substrate to impart a compressive strain fromone or both sides of a vertical fins 111, or pull the fin sidewall(s)112 upward from the substrate 110 to impart a tensile stress. Thesacrificial stressor layer 140 may be strips in parallel with thevertical fins 111 and hardmask fin templates 121, where the sacrificialstressor layer 140 forms an alternating sequence of vertical fins 111and sacrificial stressor layer 140 strips. In the various embodiments,the sacrificial stressor layer 140 may be in direct contact with thesidewalls 112 of the vertical fins 111 on each side of the sacrificialstressor layer 140.

In interpreting and understanding the present disclosure, it should beunderstood that the compressive and tensile stress is expressed inabsolute values, where such nomenclature allows comparison ofcompressive stress values without reference to or possible confusionwith the direction of the stress. For example, a compressive stress of3.0 GPa is said to be greater than compressive stress of 2.0 GPa.Depending on the residual stress inside the sacrificial stressormaterials applied, as well as the physical dimensions of the verticalfins, the stress applied to the vertical channel may be in a range ofabout 0.4 to about 2 GPa, or in the range of about 0.8 GPa to about 1.5GPa, where the stress may be tensile or compressive, although stresseslower than 0.4 GPa or greater than 2 GPa may also be achieved andapplied.

FIG. 8 also depicts a partially cut-away sacrificial stressor layer 140on a fin sidewall 112, where the top surface of the hardmask fintemplates 121 and sacrificial stressor layer 140 have beenchemically-mechanically polished to a uniform height to provide a flatsurface. A compressive strain is indicated by the downward arrow, wherethe compressive stress may be applied in the fin height direction alongthe length of the fin sidewall 112 in contact with the sacrificialstressor layer 140.

FIG. 9 is a perspective view of a cross-section of a fin-cut mask formedon the surface of the sacrificial stressor layer and the hardmask fintemplate(s) in accordance with an exemplary embodiment.

In one or more embodiments, a fin-cut mask may be formed on the topsurface of the hardmask fin templates 121 and sacrificial stressor layer140. In various embodiments, the fin-cut mask 150 may include twolayers, where a first fin-cut mask layer may be a fin-cut hardmask 160,and the second fin-cut mask layer may be a fin-cut softmask 165.

In one or more embodiments, the fin-cut hardmask 160 may be a nitride,for example, silicon nitride (SiN), a silicon oxynitride (SiON), asilicon oxide (SiO), or a combination thereof. In various embodiments,the fin-cut softmask 165 may be a resist, for example, poly methylmethacrylate (PMMA), or polydimethylsiloxane (PDMS), as would be knownin the art.

In various embodiments, the fin-cut mask 150 may be formed on the topsurface of the hardmask fin templates 121 and sacrificial stressor layer140 by forming a fin-cut hardmask 160 on at least a portion of the topsurface of the hardmask fin templates 121 and sacrificial stressor layer140, and forming a fin-cut softmask 165 on at least a portion of thefin-cut hardmask 160. The fin-cut softmask 165 may be patterned anddeveloped to expose portions of the underlying fin-cut hardmask 160. Theexposed portions of the fin-cut hardmask 160 may be removed to form afin-cut mask trench 155 exposing at least portions of the hardmask fintemplates 121 and sacrificial stressor layer 140. In variousembodiments, the exposed portions of the hardmask fin templates 121 andsacrificial stressor layer 140 may be a bottom of the fin-cut masktrench 155 across the hardmask fin templates 121 and sacrificialstressor layer 140. The fin-cut mask trench 155 may be approximatelyperpendicular (e.g., ±5°, ±3°) to the long axis of the one or morevertical fins 111 and hardmask fin templates 121.

In various embodiments, the fin-cut hardmask 160 may be removed by a dryetch, for example, a reactive ion etch (RIE).

FIG. 10 is a cross-sectional side view of a fin-cut mask on asacrificial stressor layer and hardmask fin template(s) in accordancewith an exemplary embodiment.

In one or more embodiments, the fin-cut mask 150 includes two or morelayers, where the layers may be a fin-cut hardmask 160 on thesacrificial stressor layer 140, and a fin-cut softmask 165 on thefin-cut hardmask 160, over a plurality of vertical fins 111. The fin-cuthardmask 160 may protect portions of the sacrificial stressor layer 140and hardmask fin templates 121 during a directional etching process(e.g., RIE), where the RIE is a form of plasma etching in which duringthe etching process, the surface to be etched is placed on a radiofrequency (RF) powered electrode (e.g., electrostatic chuck/waferpedestal). During RIE the surface to be etched may take on an electricalpotential that accelerates the charged etching species extracted fromplasma toward the surface, in which the chemical etching reaction takesplace in a direction normal to the surface. Other examples ofanisotropic etching that may be used at this point in the processinclude ion beam etching, plasma etching, or laser ablation.

In various embodiments, the sacrificial stressor layer 140 may apply acompressive stress to the fin sidewalls 112, and provide mechanicalreinforcement and lateral support to the vertical fin(s) 111 during adirectional etching (also referred to as a fin-cut) process. In variousembodiments, the sacrificial stressor layer 140 may apply a tensilestress to the fin sidewalls 112, and provide mechanical reinforcementand lateral support to the vertical fin(s) 111 during a directionaletching (also referred to as a fin-cut) process.

FIG. 11 is a perspective view of a cross-section of a fin trench througha fin-cut mask, vertical fins, hardmask fin templates, and sacrificialstressor layer in accordance with an exemplary embodiment.

In one or more embodiments, a fin trench 170 may be formed in thesacrificial stressor layer 140, vertical fin(s) 111, and hardmask fintemplates 121, where the fin trench 170 may be aligned with the fin-cutmask trench 155. The fin trench 170 may be formed by RIE, where thematerial exposed by the fin-cut mask trench 155 is removed. Portions ofthe sacrificial stressor layer 140, vertical fin(s) 111, and hardmaskfin templates 121 may be removed down to or below the surface of thesubstrate 110 to form the fin trench 170. The fin trench 170 mayseparate the vertical fins into columns of fin segments 116 and aplurality of sacrificial stressor layer blocks 145 adjacent to two finsegments. In various embodiments, the fin trench may extend into thesubstrate 110 to form a shallow or deep trench isolation region toelectrically separate devices formed by fins in the same column.

In various embodiments, the fin trench 170 may have a width in the rangeof about 30 nm to about 500 nm, or about 30 nm to about 100 nm, or about100 nm to about 500 nm, although narrower and wider fin trenches 155 canalso be formed. The fin segments 116 in the same row may be separatedfrom fin segments in a neighboring row by a gap about the size of thefin trench 170.

Forming a fin trench 170 may separate vertical fin 111 into a series ofshorter fin segments 116, where the fin segments 116 may be arranged incolumns along the long axis of the vertical fin 111 and separated by thefin trench 170, and in rows separated by the sacrificial stressor layerblocks 145. Each sacrificial stressor layer block 145 may be in physicalcontact with the sidewalls 112 of two fin segments in neighboringcolumns.

In various embodiments, the sacrificial stressor layer 140 providessupport to the thinner vertical fins 111 during formation of the one ormore fin trench(s) 170, while maintaining a compressive or tensilestress on the fin sidewalls 112.

In various embodiments, the fin segments in a row may have a pitch inthe range of about 30 nm to about 200 nm, or in the range of about 35 nmto about 100 nm, or in the range of about 40 nm to about 50 nm.

FIG. 12 is a perspective view of a cross-section of a fin trench throughthe vertical fins, hardmask fin templates, and sacrificial stressorlayer after removal of the fin-cut mask in accordance with an exemplaryembodiment.

In one or more embodiments, the fin-cut mask 150 may be removedsubsequent to the formation of the one or more fin trench(s) 170. Thefin-cut softmask 165 may be removed without damaging or disrupting theexposed surfaces of the sacrificial stressor layer blocks 145 and finsegments 116 by processes known in the art (e.g., stripping, ashing).The fin-cut hardmask 160 may be removed by selective etching of thefin-cut hardmask material, where the sacrificial stressor layer and/orhardmask fin templates 121 may act as etch stops. The fin-cut hardmaskmaterial may be different from the material of the sacrificial stressorlayer and/or hardmask fin templates 121. In various embodiments, thehardmask fin templates 121 may be an silicon oxynitride material (e.g.,SiON), the fin-cut hardmask 160 may be silicon nitride (e.g., Si₃N₄),and the sacrificial stressor layer 140 may be silicon dioxide (SiO₂).

In various embodiments, the hardmask fin templates 121 may be exposedafter removal of the fin-cut hardmask 160.

FIG. 13 is a perspective view of a cross-section of an anchor wallformed in the fin trenches adjacent to the vertical fins in accordancewith an exemplary embodiment.

In one or more embodiments, an anchor wall 180 may be formed in one ormore of the fin trench(s) 170. The anchor wall 180 may be formedadjacent to and in contact with one or more fin segment endwalls 117,where an anchor wall 180 may be on opposite ends of a fin segment 116.In various embodiments, the anchor walls 180 may be in a planeperpendicular to the long axis of the fin segments 116, and in contactwith one or more fin segment endwalls 117 in the same row of finsegments 116.

In one or more embodiments, the anchor wall(s) 180 may be formed by anitride material blanket deposited between the rows of fin segments 116,where an anchor wall may separate and be in contact with the endwalls117 of two fin segments 116 in the same column The nitride may be asilicon nitride (SiN). In various embodiments, the nitride may bedeposited by CVD, plasma-enhanced CVD, PVD or a combination thereof. Thenitride may be deposited over the hardmask fin templates 121 andsacrificial stressor layer blocks 145, and a CMP performed to removeexcess nitride material extending above the top surfaces of the hardmaskfin templates 121 and sacrificial stressor layer blocks 145. In variousembodiments, for example, the supporting anchor wall 180 may be composedof an oxide, such as silicon oxide (e.g., SiO₂), a nitride, such assilicon nitride (e.g., Si₃N₄), or a silicon oxynitride (e.g.,SiO_(x)N_(y)). Because the anchor wall 180 is composed of a dielectricmaterial, it may in some embodiments, be referred to as an isolationregion. For example, the anchor wall 180 that is in contact with theendwall(s) 117 of the fin segment(s) 116 may form a deep trenchisolation region between neighboring devices. In various embodiments,the anchor wall 180 may be a different material than the hardmask fintemplates 121 to allow selective etching/removal.

While not intending to be bound by theory, it is believed that theanchor walls 180 may maintain the compressive strain of the fin segments116 by securing the fin segments 116 in a reduced-height state createdby the sacrificial stressor layer 140, where the anchor walls 180 securethe height of the fin segments 116 through contact with the fin segmentendwalls 117. Similarly, it is believed that the anchor walls 180 maymaintain the tensile strain of the fin segments 116 by securing the finsegments 116 in a fix-height state created by the sacrificial stressorlayer 140, where the anchor walls 180 secure the height of the finsegments 116 through contact with the fin segment endwalls 117. Theanchor walls 180 may prevent the relaxation mechanisms through which thecompressive strain may be relieved from the vertical fin segments 116.

FIG. 14 is a perspective view of a cross-section of the anchor walls incontact with the fin segment endwalls, and exposed fin sidewalls afterremoval of sacrificial stressor layer blocks in accordance with anexemplary embodiment.

In one or more embodiments, the sacrificial stressor layer blocks 145may be selectively removed to expose the fin sidewalls 112 and hardmaskfin templates 121. The sacrificial stressor layer blocks 145 may beselectively removed by selective etching, where the etching may be a wetetch or a dry etch. In various embodiments, the etch process can be adry etch such as, for example, chemical oxide removal, or a wet chemicaletch which may employ an aqueous solution containing hydrofluoric acid(HF).

FIG. 15 is a perspective view of a cross-section of the anchor walls incontact with the fin segment endwalls, and the exposed fin sidewalls,after removal of the hardmask fin templates in accordance with anexemplary embodiment.

In one or more embodiments, the hardmask fin templates 121 may beselectively removed from the fin segments 116. The hardmask fintemplates 121 may be selectively removed by a selective RIE to exposethe top surface of the fin segments 116. In various embodiment, thehardmask fin templates 121 may be selectively removed prior to theremoval of the sacrificial stressor layer blocks 145.

FIG. 16 is a cross-sectional side view of a doped region and a bottomspacer layer on the substrate between a plurality of fin segments inaccordance with an exemplary embodiment.

In one or more embodiments, a doped region 230, which may form asource/drain of a vertical finFET, may be formed in the substrate 110.The doped region 230 may be formed in-situ or ex-situ, below where thevertical fin(s) 111 may be formed. The dopant may be provided to thedoped region(s) (i.e., source/drain region(s)) by ion implantation, andsource/drains formed by annealing the doped region(s) 230. In variousembodiments, the doped region 230 may be n-doped or p-doped. The dopedregion 230 may form a bottom source/drain. One or more doped regions 230may be formed in the substrate above which each of the one or more finsegments 116 may be formed, wherein the doped region 230 forms a bottomsource/drain for a vertical field effect transistor. It should be notedthat the source and drain can be interchangeable between the top andbottom locations of a fin segment forming the channel of a verticalfield effect transistor, where the doped region 230 in the substrate 110may act as a source or a drain for one or more of the fin segments 116,such that the doped region 230 can form a common source/drain for one ormore fin segments 116.

In one or more embodiments, a bottom spacer layer 190 may be formed onat least a portion of the exposed surface of the substrate 110 betweenthe fin segments 116. The bottom spacer layer 190 may cover thesubstrate between the rows of fin segments 116, and may cover a portionof the sidewalls of the fin segments. The front anchor wall 180 isoutside the plane of the cross-sectional view, so not shown in FIG. 16,however, the back anchor wall 180 is depicted behind the vertical finsegments 116.

In various embodiments, the bottom spacer layer 190 may be formed byhigh density plasma (HDP) CVD, PVD, or a combination thereof, where thebottom spacer layer 190 may be blanket deposited on the vertical finsegments 116 and the surface of the substrate 110. Formation of a bottomspacer 190 may involve a directional, non-conformal deposition toprovide a thicker layer of a dielectric material on surfaces normal tothe direction of the deposition than on the sidewalls along thedirection of the deposition. The spacer material on fin segmentsidewalls may be removed by a suitable wet etch process, such as BHF(buffered hydrofluoric) etch or SICONI™ etch (involving exposure of asubstrate to H₂, NF₃ and NH₃ plasma by-products). In variousembodiments, the bottom spacer layer 190 may be deposited by adirectional PVD on the surface of the substrate 110. The bottom spacerlayer 190 may be silicon nitride (SiN), silicon oxide (SiO), siliconoxynitride (SiON), a multi-layer arrangement of silicon oxide andsilicon nitride, or combinations thereof.

FIG. 17 is a cross-sectional side view of a gate structure and topsource/drains formed on the plurality of fin segments in accordance withan exemplary embodiment.

In one or more embodiments, a gate structure may be formed on the finsegments 116 by depositing a gate dielectric layer 200 on at least aportion of the exposed sidewall of the fin segments, where the gatedielectric layer 200 may also be formed on at least a portion of thebottom spacer layer 190. Undesired portions of the gate dielectric layer200 may be removed from at least a portion of the bottom spacer layer190 to form at least a portion of the gate structure on the fin segments116.

In various embodiments, the gate dielectric layer 200 may be a high-Kdielectric material that may include, but is not limited to, metaloxides such as hafnium oxide (e.g., HfO₂), hafnium silicon oxide (e.g.,HfSiO₄), hafnium silicon oxynitride (Hf_(w)Si_(x)O_(y)N_(z)), lanthanumoxide (e.g., La₂O₃), lanthanum aluminum oxide (e.g., LaAlO₃), zirconiumoxide (e.g., ZrO₂), zirconium silicon oxide (e.g., ZrSiO₄), zirconiumsilicon oxynitride (Zr_(w)Si_(x)O_(y)N_(z)), tantalum oxide (e.g., TaO₂,Ta₂O₅), titanium oxide (e.g., TiO₂), barium strontium titanium oxide(e.g., BaTiO₃—SrTiO₃), barium titanium oxide (e.g., BaTiO₃), strontiumtitanium oxide (e.g., SrTiO₃), yttrium oxide (e.g., Y₂O₃), aluminumoxide (e.g., Al₂O₃), lead scandium tantalum oxide(Pb(Sc_(x)Ta_(1-x))O₃), and lead zinc niobate (e.g.,PbZn_(1/3)Nb_(2/3)O₃). The high-k material may further include dopantssuch as lanthanum and/or aluminum. The stoichiometry of the high-Kcompounds may vary.

In various embodiments, the gate dielectric layer 200 may have athickness in the range of about 1.5 nm to about 2.5 nm.

In various embodiments, a work function layer 210 may be formed on thefin segments 116 by depositing a work function layer 210 on at least aportion of the exposed sidewall of the fin segments, where the workfunction layer 210 may also be formed on at least a portion of thebottom spacer layer 190 and/or gate dielectric layer 200. Undesiredportions of the work function layer 210 may be removed from at least aportion of the bottom spacer layer 190 and/or gate dielectric layer 200to form at least a portion of the gate structure on the fin segments116.

In one or more embodiments, a work function layer 210 may be depositedover the gate dielectric layer 200. The work function layer 210 may formpart of a gate structure, where the gate structure may be on a verticalfin segment 116.

In various embodiments, the work function layer 210 may be a nitride,including but not limited to titanium nitride (TiN), hafnium nitride(HfN), hafnium silicon nitride (HfSiN), tantalum nitride (TaN), tantalumsilicon nitride (TaSiN), tungsten nitride (WN), molybdenum nitride(MoN), niobium nitride (NbN); a carbide, including but not limited totitanium carbide (TiC), tantalum carbide (TaC), hafnium carbide (HfC),and combinations thereof.

In various embodiments, the work function layer 210 may have a thicknessin the range of about 3 nm to about 11 nm, or may have a thickness inthe range of about 5 nm to about 8 nm.

In one or more embodiments, a gate metal layer 215 may be formed on thework function layer 210, where the gate metal layer 215 may be a layerconformally deposited on the work function layer 210. In variousembodiments, the gate metal layer 215 may be tungsten (W), cobalt (Co),or a combination thereof. The gate metal layer 215 may form part of agate structure, where the gate structure may be on a vertical finsegment 116.

The portions of the gate metal layer 215 and work function layer 210 ontop of the fin segment(s) 116 may be removed by RIE or a suitable wetetch process. In various embodiments, the gate structure may wrap aroundthree sides or four sides of the vertical fin. The gate metal layer 215may be a gate electrode for a vertical finFET.

In various embodiments, when gate stacks on the vertical fin sidewalls112 are recessed from the top edge of the fin segment 116 to a reducedheight, a top spacer layer 220 may be formed on the top surface of thegate structure, where the top spacer layer 220 may be between the finsegments 116.

In one or more embodiments, a top spacer layer 220 may be formed on atleast a portion of the gate metal 215, work function layer 210, and/orgate dielectric layer 200. The top spacer 220 may be on the gatestructure opposite the bottom spacer 190. The top spacer layer 220 maybe in contact with a portion of the fin segments 116. In variousembodiments, the top spacer layer 220 may be a dielectric layer, wherethe top spacer layer 230 may be a low-K dielectric material layer. Thetop spacer layer 220 may electrically isolate the gate structure from atop source/drain. The material and deposition method can be same as thatwas used for bottom spacer formation. The excess top spacer material onthe sidewalls of the exposed vertical fins can be removed by directionalRIE etch process.

In one or more embodiments, a doped material forming a top source/drain240 may be formed on the one or more vertical fin segments 116. The topsource/drain 240 may be formed by epitaxial growth on the exposed topportions of the fin segments 116, such that the fin segments 116 and thetop source/drain 240 have the same crystal orientation. The topsource/drain may be n-doped or p-doped, and the doping may be in-situ orex-situ. The top source/drain 240 may have the same doping type as thebottom source/drain 230, and form an n-type or p-type vertical finFETwith the vertical channel.

In various embodiments, the locations of the source and drain of avertical transistor may be reversed such that the drain is on the top ofa vertical fin, while the source is at the bottom. The source may,therefore, be at the bottom or the top.

In one or more embodiments, a gate contact may be deposited on the gatemetal layer 215. The gate contact may provide an electrical contact withthe gate metal layer 215 to connect the gate structure to an electricalline (e.g., word line, signal line, etc.).

In one or more embodiments, an interlayer dielectric (ILD) layer 250 maybe formed between the anchor walls 180 on opposite ends of the finsegments 116. The ILD may be an insulating dielectric material, whichmay be a low-K dielectric material, for example, porous silicon dioxide,carbon-doped silicon dioxide, or fluorine doped silicon dioxide.

FIG. 17 also shows a cross-sectional side view of a vertical fin fieldeffect transistor having a strained channel, a gate structure with agate electrode, and source/drain region on the vertical fin inaccordance with another exemplary embodiment.

In one or more embodiments, one or more vertical fins 111 or finsegments 116 may be removed as dummy fins to increase the distancebetween two neighboring fins/segments to create an arrangement offins/segments that may form one or more separate devices, for example,complementary metal-oxide semiconductor devices. The devices may bemulti-fin devices, where two or more fins may share a common dopedregion 230 in the substrate 110 and have electrically coupled topsource/drains 240 and/or electrically coupled gate structures.

Having described preferred embodiments for the fabrication of verticalfield effect transistor structure with strained channels (which areintended to be illustrative and not limiting), it is noted thatmodifications and variations can be made by persons skilled in the artin light of the above teachings. It is therefore to be understood thatchanges may be made in the particular embodiments disclosed which arewithin the scope of the invention as outlined by the appended claims.Having thus described aspects of the invention, with the details andparticularity required by the patent laws, what is claimed and desiredprotected by Letters Patent is set forth in the appended claims.

What is claimed is:
 1. A method of forming a vertical fin field effecttransistor (vertical finFET) with a strained channel, comprising:forming one or more vertical fins on a substrate; forming one or moredoped regions in the substrate above which each of the one or morevertical fins is formed, wherein each of the one or more doped regionsforms a bottom source/drain for one vertical field effect transistor;forming a sacrificial stressor layer adjacent to the one or morevertical fins, wherein the sacrificial stressor layer imparts a strainin the adjacent vertical fins; forming a fin trench through one or morevertical fins and the sacrificial stressor layer to form a plurality offin segments and a plurality of sacrificial stressor layer blocks; andforming an anchor wall adjacent to and in contact with one or more finsegment endwalls.
 2. The method of claim 1, further comprising forming atop source/drain on a top surface of the one or more vertical fins,where the vertical fin(s) form a channel of the vertical finFET.
 3. Themethod of claim 1, further comprising removing the plurality of thesacrificial stressor layer blocks, wherein the anchor walls adjacent toand in contact with the one or more fin segment endwalls maintains thestrain of the adjacent fin segments after removal of the sacrificialstressor layer blocks adjacent to the fin segment with the adjacentanchor wall.
 4. The method of claim 1, wherein the one or more verticalfins are formed by forming a hardmask layer on the substrate and a photomask layer on the hardmask layer, patterning the photomask layer andetching the hardmask layer to form one or more hardmask fin templatesdefining the width, length, and pitch of the one or more vertical fins.5. The method of claim 1, wherein the sacrificial stressor layer is aflowable oxide or spin-on-glass.
 6. The method of claim 1, wherein theanchor wall is a silicon nitride.
 7. The method of claim 1, furthercomprising forming a fin-cut mask on a top surface of the one or morevertical fins and sacrificial stressor layer, and forming one or morefin-cut mask trench(es) in the fin-cut mask to define the position andwidth of the fin trench.
 8. The method of claim 7, further comprisingforming a gate structure on the one or more vertical fins.
 9. A methodof forming a vertical finFET with a strained channel, comprising:forming a plurality of vertical fins on a substrate; forming asacrificial stressor layer adjacent to the vertical fins, wherein thesacrificial stressor layer is in contact with the sidewalls of theadjacent vertical fins, and imparts a compressive strain to the adjacentvertical fins; separating the vertical fins into columns of fin segmentsand a plurality of sacrificial stressor layer blocks each adjacent totwo fin segments; forming an anchor wall in each fin trench adjacent toand in contact with one or more fin segment endwalls; and removing theplurality of the sacrificial stressor layer blocks.
 10. The method ofclaim 9, further comprising forming a top source/drain on a top surfaceof the one or more vertical fins.
 11. The method of claim 9, furthercomprising forming one or more doped regions in the substrate abovewhich each of the one or more vertical fins is formed, wherein the dopedregion forms a bottom source/drain for a vertical field effecttransistor.
 12. The method of claim 9, wherein the sacrificial stressorlayer is a flowable oxide.
 13. The method of claim 9, wherein thesacrificial stressor layer is formed by CVD.
 14. The method of claim 9,wherein the compressive strain induced in fin segments is in the rangeof about 0.4 GPa to about 2 GPa, and wherein the anchor wall maintainsthe strain of the adjacent fin segments after removal of the sacrificialstressor layer blocks adjacent to the fin segment with the adjacentanchor wall.